The focus of the research program proposed here is to study the role of physical attractiveness in the development of cognitions of others and in the enactments of specific behaviors by infants, children, and adolescents who vary in level of physical attractiveness. First, a longitudinal study of infants and their mothers is proposed to examine mother-infant behavior patterns as a function of physical attractiveness to the infant. Second, we shall conduct a series of studies with children aged 6 to 16. In these studies we will investigate: 1) behavioral differences between attractive and unattractive children; 2) differential treatment by peers as a function of appearance; and 3) the developmental course of these behaviors exhibited by and toward attractive and unattractive children. Finally, we propose to examine the social cognitions and liking preferences of these children and adolescents so that we may understand the relationships between social cognitions and social behaviors. Cognitive-developmental theory and a transactional model of development provide the theoretical rationale for these studies.